1. Field of the Invention
The present invention relates to a technology for accessing data on a storage medium by controlling a head, with a capability of retracting the head at an appropriate speed.
2. Description of the Related Art
A magnetic disk drive is mainly used as an auxiliary storage device of a general-purpose computer and for a business-purpose device that requires high-capacity random access data recording. Furthermore, use of the magnetic disk drive as a general household appliance has increased recently, with an advance of digitalization of household appliances and an increase of applications to record data such as audio-visual data as digital data (for example, a hard disk video recorder and a portable music reproducing device).
However, when the magnetic disk drive receives a strong impact due to a fall, a head collides with a disk surface and the disk surface gets scratched, and data reading and writing may become impossible. Particularly, falls of the magnetic disk drive while it is in operation cause the magnetic disk drive to become easily out of order. Therefore, when handling a product that includes a magnetic disk drive for a portable application, an attention had to be paid to avoid giving a strong impact to the product.
Japanese Patent Application Laid-Open No. 2002-8336 discloses a technology that uses a fall sensor to prevent damages caused by falls of the magnetic disk drive and retracts the head from the disk surface when a free fall of the magnetic disk drive is detected.
However, the conventional technology has a problem of ramp abrasion and contamination generation since a large amount of current is applied to an actuator to promptly retract the head from the disk surface when falls of the magnetic disk drive were detected and the speed during head retraction became unnecessarily high.
The conventional technology also has a problem of a limited number of times the head can be retracted since the head and the ramp made contacts due to the excessive speed and the head and the ramp were severely scratched.